In the referenced Bradshaw et al. patent, there is described and claimed a system for sorting articles of varying physical characteristics, including machinable mail flats. In operation, the incoming mail flats are clipped to a carrier device at an induction station and subsequently the carrier's magnetic stripe is encoded with a destination code based, for example, on the ZIP code. The flat then enters a conveyor distribution system which reads the escort memory data on the carrier's stripe and directs the flat via appropriate gating to a storage destination or output accumulation rack to await further sorting or outputting from the system. Such a system requires a sizable space allocation to accommodate the large numbers of storage locations.
The recirculation buffer subsystem described and claimed in the Ouimet et al. patent provides a solution to the storage space problem which directs itself to small and medium size Post Offices. Thus, in accordance with the last mentioned patent, one or more recirculating buffers are incorporated between the induction stations and the output accumulation racks of the aforementioned Bradshaw et al. system. The recirculating buffer offers a means of temporarily storing flats on carriers such that any flat may be taken out of storage independently of any other. This is accomplished by providing a closed serpentine conveyor path such that all flats are continuously moving. If a specific flat is requested, the carrier and the flat attached thereto are caused to exit the buffer after passing a reader which identifies the flat in accordance with the destination data stored on the carrier escort memory. A record is kept by the system computer of the data associated with all of the flats in the buffer in order that control may be provided. The computer functions to maintain a balance between output and input and provides to the output packaging, or traying subsystem, the most productive stack sizes available in the system. This is accomplished through the establishment of a hierarchy of priorities, such as the flat count or stack thickness per destination.
In addition to the basic sorting function required in mail-handling applications, a sequencing operation in which items are placed in sequence order, assumes primary importance. In the past, sequencing has often involved time-consuming and inefficient methods. The present invention expands upon the recirculation buffer subsystem of the Ouimet et al. patent to provide an effective, high-speed sequencing capability.